Chemistry of electron-rich conjugated polyenes VI. A comparative study of the rates and mechanism of [4 + 2]-cyclo-additions between alkoxy-1,3-butadienes and β,β-dicyanostyrenes

✍ Scribed by A. A. Broekhuis; J. W. Scheeren; R. J. F. Nivard

• Book ID: 104588315
• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 547 KB
• Volume: 100
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19811000403

✦ Synopsis

Abstract

The kinetics of [4 + 2] cycloadditions in several solvents have been studied for reactions between ring‐substituted β,β‐dicyanostyrenes (2a–j) and a series of methoxybutadienes (1a–e), differing in electron‐donating properties, conformational preference and polarity. All reactions studied gave linear Hammett plots with positive p values when log k/k~0~ values were plotted against σ^+^ substituent constants. Solvent effects appeared to be small.

The results have been discussed on the basis of differences in the HOMO‐LUMO interaction and in conformational factors for differing pairs of reactants. In this way more detailed insight has been obtained into variations in the nature (olefin‐like or product‐like) and polarity of the transition state of these reactions.